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Earthen sites (i.e., ancient earthen buildings) with important historical, cultural, artistic, social, and scientific value have been seriously damaged. Soil treatment with chemical additives can decrease the degradation rate of earthen sites. In the past, polyvinyl alcohol (PVA) and quicklime as chemical additives were studied separately for the protection of earthen sites. In arid and semi-arid northwest China, the early strength of the lime-treated soil may be insufficient due to an inappropriate reaction environment, and the PVA as the additive can quickly increase the soil strength. However, calcium carbonate has been proven to not be decomposed for hundreds of years, while there is still a lack of experimental evidence to show that the PVA cannot be decomposed in decades. The PVA and lime as the additives show the potential to make up for the defects each other. Therefore, the physical and mechanical properties of the PVA and lime composite soil are analysed, and the microscopic properties of the composite soil are discussed in this study. The results show that the addition of the PVA decreases water vapour permeability and pore size, which causes a delay in the carbonization reaction of lime, but it acts as a cementing agent to improve soil strength before the lime appropriately reacts. The addition of quicklime can decrease the hydrophobicity of the PVA-treated soil. The mixing of these two materials is conducive to the colour control of the sample. For the composite soil applied to earthen sites in northwest China, the optimal ratio is 10% lime and 1.0% PVA. [ABSTRACT FROM AUTHOR]

Modelling the lime requirement (LR) is a fast and efficient way to determine the amount of lime required to obtain a pH that can overcome the adverse effects caused by soil acidification. This study aimed to model the LR based on the properties of soil and lime. A total of 17 acidic soils and 39 lime samples underwent soil–lime incubation in the laboratory. The predictive equations for the LR (t ha−1) were modelled using ∆pH (the difference between the target pH and initial pH), the neutralizing value (NV, mmol kg−1) of lime, soil pH, soil clay content (%), soil bulk density (BD, g cm−3), and the depth of soil (h, cm) as the factors in an exponential equation. The generic predictive equation, L R = ∆ p H × e − 3.88 − 0.069 × N V + 0.51 × p H + 0.025 × C l a y × B D × h , was validated as the most reliable model under field conditions. Simplified predictive equations for different soil textures when limed with quicklime and limestone are also provided. Furthermore, the LR proportions provided by hydrated lime, quicklime, limestone, and dolomite in commercially available lime can be expressed as 0.58:0.64:0.97:1.00. This study provides a novel and robust model for predicting the amount of lime product containing components with different neutralizing abilities that are required to neutralize soils with a wide range of properties. It is of great significance to agronomic activities and soil remediation projects. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) pollution poses a growing threat to rice production in acidic paddies. In south China, a common agricultural practice involves the combined utilization of Chinese milk vetch (M) and rice straw (R). However, it is unclear how the addition of lime to these amendments affects Cd bioavailability and accumulation in soil. Control (CK), chemical fertilizer (F), Chinese milk vetch + rice straw + chemical fertilizer (MRF), and Chinese milk vetch + rice straw + chemical fertilizer + lime (MRFL) treatments were applied to develop a kind of green, efficient, and practical amendment for acidic paddies. We conducted a microplot experiment to explore Cd immobilization in paddy soil and the Cd content in rice grains with these treatments. The results showed that compared with F, the rice Cd in the MRF and MRFL treatments were significantly decreased by 51.7% and 65.2% in early rice and 23.0% and 43.3% in late rice, respectively. Both the MRF and MRFL treatments significantly reduced soil available Cd and weak acid-extractable cadmium (Aci-Cd) concentrations and increased soil organic matter (SOM), exchangeable cation concentrations, and pH, which converted Cd into a stable form in soil. In addition, the MRF and MRFL treatments increased soil pH value by reducing soil exchangeable hydrogen ion concentration (E-H). Additionally, recombination of Cd forms was the primary factor in the reduction in available Cd concentration according to partial least squares path modeling (PLS-PM) analysis. The Cd concentration of rice grains was primarily associated with soil available Cd, soil pH value, and SOM. Overall, these results provide useful data and novel insights into reducing rice grain Cd in south China. [ABSTRACT FROM AUTHOR]

Plant functional traits can serve as indicators of plant resource-use strategies in response to environmental changes. Plants growing in acidified soil exhibit conservative traits and limit growth, but there is still little known about changes in above- and belowground functional traits and their coordination under alleviation of soil acidification. Here, we conducted a pot experiment on raising soil pH by liming in Chinese fir (Cunninghamia lanceolata) saplings in southern China. The experiment involved in two degrees of acidified soil (Mild, pH = 4.3; Severe, pH = 3.6) and three liming treatments: Control (CK, 0), low liming treatment (L, 1000 kg CaO hm−2) and high liming treatment (H, 4000 kg CaO hm−2). We measured 22 above- and belowground functional traits of Chinese fir including allocation, morphological, photosynthetic, and chemical traits to assess their response to liming. The results show that liming enhanced aboveground mass fraction and total leaf area (TLA), and reduced construction cost (lower C concentration). However, specific leaf area (SLA), nutrient concentrations of N and P, and photosynthetic rate (Pn) remained unchanged. These results suggest that aboveground components exhibited acquisitive strategies in response to liming with greater TLA and lower construction cost. Moreover, liming reduced root mass fraction (RMF), increased specific root length (SRL), specific root area (SRA), and root N and Ca nutrient concentrations. These results suggest that belowground components also exhibited acquisitive strategies through constructing longer and thinner roots with greater metabolic rates. Our findings show that liming shifts above- and belowground resource-use strategies of Chinese fir from conservative to acquisitive. These changes in functional traits support the ability of Chinese fir to grow rapidly in response to alleviation of soil acidification. Our research not only contributes to a deeper understanding of plant adaptation mechanisms in the face of environment changes but also provides valuable insights for improving carbon sequestration of plantations in subtropical China. • 22 functional traits of Chinese fir were measured to assess their response to liming. • Liming elevated total leaf area and reduced leaf construction cost. • Liming elevated specific root length, specific root area and root N concentration. • Liming shifts resource-use strategies of Chinese fir towards acquisitive. [ABSTRACT FROM AUTHOR]

Inadequate provision of winter and early spring forage is a major problem for ruminant production in Yunnan Province, China. Temperate legumes (e.g., white clover) combined with perennial grasses (e.g., perennial ryegrass, cocksfoot) have the potential to fill this feed gap for livestock production when high fertiliser inputs are maintained. In commercial practice, however, these legume/grass pastures perform poorly and lack persistence due to poor fertiliser management. This paper describes a low-input fertiliser strategy developed to maintain productive pastures on moderately acid (ph = 5.3) Hapludult (red earth) soils in Malong county, Yunnan. Since initial soil tests showed major deficiencies of phosphorus (P) (<6 mg kg-1 Bray P) and potassium (k) (16 mg kg-1), a three-replicate experiment was done that included four rates of fused calcium magnesium phosphate (caMgP) fertiliser (0, 500, 1000 and 1500 kg ha-1 yr-1), four rates of potassium sulphate (K2SO4) fertiliser (0, 100, 200 and 300 kg ha-1 yr-1) and four rates of quick (or burnt) lime (0, 500, 1000 and 1500 kg ha-1 yr-1) to define a low-input P, C and ca strategy for white clover/cocksfoot/ perennial ryegrass pasture. Our results indicated that the lowest P rate (117 kg P ha-1 3 yr-1) when combined with adequate K (123 kg k ha-1 3 yr-1) and ca (1.3 t Ca ha-1 3 yr-1) inputs produced 86% of the white clover production and 96% of the cocksfoot production measured at the highest P rate. Potassium had no effect on pasture production when applied without P, but had a significant effect on the yield of white clover when combined with P fertiliser. Lime application had no effect on either pasture production or the levels of available soil P and K, but it did raise soil pH to above 6.5. Potassium deficiency was more serious for white clover than for the grasses, and an annual application of c. 50 kg K ha-1 was needed to retain white clover as a stable pasture component on these soils. We conclude from our results that it is technically feasible to make introduced temperate pastures on acid soils in Malong county productive through an annual application of a modest fertiliser rate comprising 500 kg ha-1 of fused CaMgP and 100 kg ha-1 of sulphate of potassium to overcome nutrient deficiencies. Due to the complexity of acid soil problems, we recommend a three-step process for successful pasture management: (1) undertake soil tests to identify the specific soil properties and nutrient deficiencies that are likely to limit pasture productivity; (2) choose pasture combinations that correctly match pasture species with existing soil constraints; and (3) tailor fertiliser strategies to specifically meet the nutrient requirements of the chosen pasture combination. Using this approach we recommend that low inputs of P and K be applied annually and that perennial ryegrass be deleted from the temperate pasture species combination recommended for moderately acid soils in Malong county. [ABSTRACT FROM AUTHOR]